Thank you for the suggestion! I tried duplicity, but it uses full+differential scheme and I cannot prune old backups unless I start a new chain. 7zip with encry

Thank you for the suggestion! I tried duplicity, but it uses full+differential scheme and I cannot prune old backups unless I start a new chain. 7zip with encryption does not do even that, but I went for it for the simplicity's sake for now, because duplicity did not work well with NTFS volumes.